title: Differentiation of recurrent tumor and posttreatment changes in head and neck squamous cell carcinoma: application of high b-value diffusion-weighted imaging.
abstract: OBJECTIVE
  High b-value DWI has been expected to have an additional diagnostic role and demonstrated some promising results in head and neck cancer. The aim of this study was to evaluate the diagnostic performance of DWI at a high b-value (b=2000 s/mm(2)) compared with a standard b-value (b=1000 s/mm(2)) and the ratio of ADC values of high and standard b-values for their ability to differentiate between recurrent tumor and posttreatment changes after the treatment of head and neck squamous cell carcinoma.
  
  
  METHODS
  A total of 33 patients diagnosed with head and neck squamous cell carcinoma were enrolled in the present study; all had contrast-enhancing lesions on follow-up MR imaging. All patients underwent single-shot echo-planar DWI at b=1000 s/mm(2) and b=2000 s/mm(2), and corresponding ADC maps were generated (ADC1000 and ADC2000, respectively). The mean ADC1000, ADC2000, and ADCratio (ADCratio = ADC2000/ADC1000 × 100) values were evaluated within a manually placed ROI with contrast-enhanced T1-weighted images as references. For the statistical analysis, we performed a Student t test and multivariate logistic regression.
  
  
  RESULTS
  The mean ADC1000 in recurrent tumor was significantly lower than that in posttreatment changes (P < .001), whereas the mean ADC2000 resulted in no significant difference (P = .365). The mean ADCratio was significantly higher in recurrent tumor than that in posttreatment changes (73.5 ± 7.2% vs 56.9 ± 8.8%, respectively; P < .001). Multivariate logistic regression analysis revealed that the ADCratio was the only independently differentiating variable (P = .024). The sensitivity, specificity, and accuracy of ADCratio were 95.0%, 69.2%, and 84.8%, respectively, by use of the optimal cutoff value of 62.6%.
  
  
  CONCLUSIONS
  We suggest that the ADCratio calculated from the ADC1000 and ADC2000 is a promising value for the differentiation of recurrent tumor and posttreatment changes in head and neck squamous cell carcinoma.
authors.affiliation: Department of Radiology Seoul National University College of Medicine, Seoul, Korea.
authors.forename: I
authors.initials: I
authors.lastname: Hwang
authors.forename: S H
authors.initials: SH
authors.lastname: Choi
authors.forename: Y-J
authors.initials: YJ
authors.lastname: Kim
authors.forename: K G
authors.initials: KG
authors.lastname: Kim
authors.forename: A L
authors.initials: AL
authors.lastname: Lee
authors.forename: T J
authors.initials: TJ
authors.lastname: Yun
authors.forename: J-h
authors.initials: JH
authors.lastname: Kim
authors.forename: C-H
authors.initials: CH
authors.lastname: Sohn
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D002294:Carcinoma, Squamous Cell / Q000473:pathology* / Q000628:therapy*; D003937:Diagnosis, Differential; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006258:Head and Neck Neoplasms / Q000473:pathology* / Q000628:therapy*; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology* / Q000517:prevention & control*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D000077195:Squamous Cell Carcinoma of Head and Neck; D016896:Treatment Outcome